<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <script>
        /**
         * 同:  1  7  
         * 宏   0
         * 微   
         * 1 7  2 3 8 4 5 6 0
         * 1 7 2 3 4 5 8 6 0
         * 1 7 2 3 8 4 6 5 0 
         * 
         * 输出： 1  7  2  3 8 4  6  5 0
         */   

        setTimeout(() => {
            console.log("0")
        }, 0)
        new Promise((resolve, reject) => {
            console.log("1")
            resolve()
        }).then(() => {
            console.log("2")
            new Promise((resolve, reject) => {
                console.log("3")
                resolve()
            }).then(() => {
                console.log("4")
            }).then(() => {
                console.log("5")
            })
        }).then(() => {
            console.log("6")
        })

        new Promise((resolve, reject) => {
            console.log("7")
            resolve()
        }).then(() => {
            console.log("8")
        })
    </script>
</body>

</html>